A conventional radio communication system that has a base station control apparatus uses a macrodiversity technique to obtain diversity effects by transmitting data in the same path from a plurality of base station apparatuses to a certain mobile station apparatus. In a radio communication system that uses the CDMA (Code Division Multiple Access) system in IMT-2000, a diversity communication technique is introduced whereby a base station control apparatus transmits sound, packets, control information, and other signals to a single mobile station apparatus via a plurality of base station apparatuses. This technique ensures high-quality communication through a diversity benefit that is obtained by a process in which the transmission signal is duplicated in the base station control apparatus, and the duplicated transmission signal is transmitted in parallel to the plurality of base station apparatuses via a plurality of wire transmission lines, and then transmitted from the plurality of base station apparatuses to the mobile station apparatus via a radio propagation channel.
FIG. 1 is a block diagram showing the structure of the conventional radio communication system 10. As shown in FIG. 1, the conventional radio communication system 10 has a core network 11, base station control apparatus 12, a plurality of base station apparatuses 13-1, 13-2, and mobile station apparatus 14. The system has the same structure when there are two or more base station apparatuses 13.
Core network 11 and base station control apparatus 12 are connected by wire transmission line 15, and each of the plurality of base station apparatuses 13-1, 13-2 is independently connected to base station control apparatus 12 by wired transmission lines 16-1, 16-2, respectively. Mobile station apparatus 14 also communicates with the plurality of base station apparatuses 13-1, 13-2 via radio propagation channel 17-1, 17-2, respectively.
Following is a description of the operations that occur when data are transmitted from core network 11 to mobile station apparatus 14 in the type of structure described above.
First, core network 11 transmits a data frame to base station control apparatus 12 via wired transmission line 15. Base station control apparatus 12 that receives the data frame duplicates the received data frame for transmission to the plurality of base station apparatuses 13-1, 13-2 and transmits the duplicated data frame to base station apparatuses 13-1, 13-2 via wired transmission lines 16-1, 16-2, respectively.
The plurality of base station apparatuses 13-1, 13-2 adds control information to the received data frames to form radio frames, and transmits the radio frames to mobile station apparatus 14 via radio propagation channels 17-1, 17-2.
Next, in mobile station apparatus 14, the transmission lag in radio propagation channels 17-1, 17-2 between the received radio frames is corrected, the phases of the radio frames are aligned, the radio frames are synthesized, and the received data are reconstructed from the synthesized signals.
In the conventional radio communication system 10 described above, higher quality communication is achieved by causing mobile station apparatus 14 to receive the same data frames via a plurality of radio propagation channels 17-1, 17-2. Even when phasing or another factor is in effect, e.g., when the propagation environment of the first radio propagation channel 17-1 has deteriorated, higher quality communication can still be achieved by synthesizing the data frame received via the other radio propagation channels 17-2.    Non-patent Document 1: 3GPP TS 25.427 UTRAN Iub/Iur Interface User Plane Protocol For DCH Data Streams